UPDATE: A manhunt is under way across Europe after German authorities identified Tunisian Muslim man, Anis Amri (23) and said that the suspect is believed to be armed and dangerous. He is wanted for questioning in connection to the deadly truck attack at a Christmas market in Berlin on December 19. He is also alleged to have murdered to murdered a Polish truck driver, whose body was found in the cab of the truck that plowed into a crowd, killing 11 and wounding others. Amri had already been under surveillance by police, who suspected that he was dealing in firearms. Germany is offering a reward of up to €100,000 (£84,000; $104,000) for information leading to his arrest.
The so-called "Islamic State" (IS) on Tuesday said the driver of the truck that plowed into a Christmas market in Berlin on Monday evening was "targeting citizens of the Crusader coalition," according to the group's news agency Amaq.
Earlier, German prosecutors announced the release of a 23-year-old Pakistani detained in connection with the truck attack, citing a lack of evidence.
On the evening of December 20, following the announcement that the suspect had been released, German Interior Minister Thomas de Maiziere told broadcaster ZDF that "it is true that one cannot rule out that the perpetrator is still at large." He also warned that it was too early to draw political conclusions from the incident.
Authorities had arrested the asylum seeker on suspicion of driving the truck, which killed 12 and injured at least 48.
'Wrong man' detained
Even before de Maiziere made his statement, Berlin police had admitted that they may have apprehended the wrong suspect and warned the public to remain attentive and vigilant.
"As far as I know, it is in fact uncertain whether that really was the driver," Berlin's police chief Klaus Kandt said at a press conference.
Germany's "Die Welt" newspaper had also quoted security sources as saying the arrested man was not believed to be the perpetrator.
A police spokesperson reportedly told the paper: "We have the wrong man, and therefore a new situation. The true perpetrator is still armed, at large and can cause fresh damage."
Speaking to German news agency dpa following the press conference, Kandt said investigators were continuing to inspect the truck used in the attack, searching for fingerprints, blood and smudge marks. "I estimate that the current investigation will take somewhat longer," he said, adding that it could take a few days before new evidence comes to light.
A Polish man who was in the passenger seat of the crashed truck was found shot dead at the scene.
'An act of terrorism'
Germany's two top prosecutors confirmed on December 20 that investigators are indeed treating the incident as an act of terrorism. Prosecutor Peter Frank said that, given the target and nature of the attack, the incident pointed towards Islamist extremist motives.
Frank said the attack was reminiscent of July's terrorist attack in Nice, France, and of the "modus operandi" deployed by Islamist terror groups.
However, echoing Berlin's police officials, Frank also acknowledged that the detained suspect "may not have been the perpetrator or belong to the group of perpetrators."
German Chancellor Angela Merkel, who visited the scene of the attack on Tuesday afternoon, also referred to the incident as a "terrorist act." Speaking before the police made their admission about the detained suspect, Merkel acknowledged that the crime might have been committed by an asylum seeker.
Risk remains high
The head of Germany's Criminal Police Agency, Holger Münch, said he could not rule out if further suspects were still at large, and therefore warned of further attacks on the back of Monday's incident. In the aftermath of such an event, "there's always a heightened risk of significant further attacks," he said.
"We are naturally on high alert and are investigating in all directions," Münch added.
He also revealed that six of the 12 people killed have been identified as Germans. He could not, however, identify the nationalities of the other six.
New Year's celebrations to go ahead
Also speaking on December 20, Berlin's State Interior Minister Andreas Geisel confirmed that the city's New Year's Eve celebrations will go ahead under an increased security presence. Every year, hundreds of thousands of revelers ring in the New Year in front of Berlin's Brandenburg Gate.
He said the city will review all of its security measures before the celebrations on December 31.
Frauke Petry, who leads the populist Alternative for Germany Party (AfD) is believed to have a fair chance at defeating the incumbent chancellor of Germany, Angela Merkel, in next year's general election. Petry said in the aftermath of the latest attack that Germany is no longer safe. She blamed the government for the attack, saying that more could have been done. "The milieu in which such acts can flourish has been negligently and systematically imported over the last one and a half years,” she said.
“On such a sad day, the AfD does not attach any importance to keeping right. Our migration limits should be finally controlled. Germany is no longer safe.”
The German Christmas market is a tradition dating back to the medieval era. The market in Munich, for example, is more than 700 years old.
Even members of Merkel's party are in a bellicose mood. Klaus Boullion, who is the Interior Ministry for the German state of Saarland, told a radio interviewer that Germany is now in a “state of war.” Like other politicians, across the various parties, he has blasted Merkel's open-door immigration policy and perceived laxity in dealing with criminal acts by migrants. Speaking to Saarland radio, Boullion said, “We must state that we are in a state of war, although some people who want to see only the good can not see.” Calling for militarized law and order, he added, “We will take it wherever we think it is necessary. That means long-range weapons, short weapons, machine guns, even if this sounds martial.”